Bruce, you may want to experiment with the height of the rears and sides as well before making final decision. In my experience getting them lower improved things considerably. I ended putting them just barely above the ear level, maybe 15cm or so above ears when seated. The sound change from vertical adjustment was more than the change from moving them laterally. I would also experiment with moving the sides a bit further back so that they are not as much in front of the back seat. but rather at most directly to the side of it - at least in line with the front edge of the seat. Again "my experience" has been that placing side channels anywhere ahead of the listening position destroys the surround "magic".
